Re: Bizarre missing changes (git bug?)

[Linus Torvalds <torvalds@linux-foundation.org>]

On Tue, 29 Jul 2008, Roman Zippel wrote:
> 
> I'm not dismissing it, but your focus is on how to get this result.

No, you misunderstand.

My focus is really on one single thing:

 - performance

with a smaller focus on the fact that I simply don't see how it's 
_possible_ to do better than our current all-or-nothing approach of 
simplification (eg either extreme simplification or none at all: nothing 
or --full-history).

So here's my challenge again, which you seem to have TOTALLY MISSED.

Make this be fast:

	time sh -c "git log <filename> | head"

nothing else matters. If you can make that one be fast, I'm happy. 

And that "| head" is really very fundamentally important. The important 
thing from a performance standpoint is not how long the _whole_ "log" 
takes. The important thing is how fast it _feels_, and that is directly 
tied to how fast it starts outputting the data.

Put another way: I _know_ how to simplify things. Trust me, Roman. That's 
not the problem. But doing it incrementally is really really hard, to the 
point that I actually believe that it is impossible to do. 

And doing it after-the-fact is simply not interesting. We could trivially 
(well, _fairly_ trivially) do it when we do the topology sort. But I have 
long long tried to teach people _not_ to do the topo sort inside the core 
git machinery, exactly because it is a horrid thing from an interactivity 
standpoint.

In fact, you can see what I'm talking about by trying --topo-order in the 
above timing test.

Really. Just _try_ it. And if you still don't understand what I'm talking 
about, I don't know what to say.

> > And quite frankly, I've seen that behaviour from you before, when it comes 
> > to other things.
> 
> What exact behaviour is that? That I dare to disagree with you?

No. The fact that you like arguing _pointlessly_, and just being abrasive, 
without actually helping or understanding the big picture. I'm thinking 
back on the whole scheduler thing. You weren't arguing with _me_, but you 
had the same modus operandi.

			Linus